Means for taking samples out of a reaction vessel containing alkaline liquid under pressure

ABSTRACT

For taking samples from a sulphate digester which contains alkaline liquid under pressure, a circuit is provided with a pump from which a branch conduit leads through valves to the bottom of a container for the alkaline liquid. A valve pipe leads downwardly from the top of the container to the atmosphere. There is also an outlet from the container below the top thereof. A sampling vessel is constituted by a pipe which opens at the top at an intermediate point within the container and communicates through a valved pipe with an analysis vessel. A water holder can be used for rinsing the analysis vessel and the container.

United States Patent 11 1 Englund et al.

Bengt Nilsson, all of Vasteras, Sweden [73] Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden 22 Filed: Feb. 16,1972

211 Appl. No.2 226,864

[30] Foreign Application Priority Data Feb. 22, 1971 Sweden 2206/71 [52] U.S. Cl. 73/422 R, 73/422 TC [51] Int. Cl. G0ln UN [58] Field of Search 73/421 R, 421 B, 422 TC [56] References Cited UNITED STATES PATENTS 2,082,299 l/l937 Nonhebel et a1 73/421 B [451 May28, 1974 3,653,265 4/l972 Vallino et al 73/42] H Primary Examiner-S. Clement Swisher [5 7 ABSTRACT For taking samples from a sulphate digester which contains alkaline liquid under pressure, a circuit is provided with a pump from which a branch conduit leads through valves to the bottom of a container for the alkaline liquid. A valve pipe leads downwardly from the top of the container to the atmosphere. There is also an outlet from the container below the top thereof. A sampling vessel is constituted by a pipe which opens at the top at an intermediate point within the container and communicates through a valved pipe with an analysis vessel. A water holder can be used for rinsing the analysis vessel and the container.

3 Claims, 2 Drawing Figures 1 MEANS FOR TAKING SAMPLES OUT OF A REACTION VESSEL CONTAINING ALKALINE LIQUID UNDER PRESSURE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a device for taking samples from a reaction vessel containing alkaline liquid under pressure, such as a sulphate digester.

2. The Prior Art In the manufacture of sulphate pulp, wood is treated with an alkaline liquid containing sodium hydroxide and sodium sulphide in a digester at increased temperature, in the final stage usually about 170C, and under increased pressure, usually about 6 atm., for several hours. In order to achieve the desired final product it is of decisive importance that the digestion is performed under carefully controlled conditions.

During the digestion process the cellulose fibres are liberated from the wood by release of the lignin. This purpose is achieved by the digestion liquid and its content of sodium hydroxide and sodium sulphide thus gradually decreases and its ability to absorb ultraviolet light gradually alters. By taking samples from the digesill tion liquid, either periodically or continually during the process, and analysing these samples it is possible to follow the progress-of the digestion process and make necessary adjustments in the digestion conditions, for example to alter the temperature or adjust the composition of the liquid and to stop the process when the desired final product has been obtained. It is also possible to calculate in advance how long the process will take. The samples can be analysed by titration with acid as well as measuring the pH value or the electrical conductivity to determine the effective alkalinity, by titration with iodine or with silver nitrate or some other heavy metal salt to determine the sulphide content and by measuring the absorption of ultraviolet light to determine the lignin content. Sampling and analysis of the digestion liquid can be carried out automatically, for example with the help of a computer which controls the digestion process by impulses to the adjustment members for this process.

- If the digestion process is to be controlled in the desired manner and interrupted at the right moment, the sampling must be performed quickly and accurately. However, there have proved to be considerable problems in achieving such sampling. This is particularly the case with automatic analyses where no manual intervention is possible. The problems are caused by the great tendency of the alkaline liquid to produce foam when its pressure alters from that prevailing in the digester to atmospheric pressure in the sampling vessel.

SUMMARY OF THE INVENTION The present invention relates to a means by which these problems of foam are eliminated. The invention can be used with advantage for taking samples from reaction vessels other than sulphate digesters containing alkaline liquid under pressure, for example from autoclaves for fat splitting.

The present invention relates to a means for taking samples from a reaction vessel containing alkaline liquid under pressure, for example a sulphate digester, characterized in that it comprises a container provided with an inlet for the alkaline liquid arranged in the container, said inlet being connected by an openable and closable connection conduit to the reaction vessel, with an openable and closable liquid outlet for the alkaline liquid arranged in the lower part of the container and with an adjustable gas connection arranged in the upper part of the container, said gas connection being connected to a gas supply of large volume and lower pressure than the pressure in the reaction vessel, preferably to the outer atmosphere, and with an entrance arranged between the liquid outlet and the gas connection of a sampling vessel located below the entrance for collecting alkaline liquid supplied to the container.

By means of the adjustable gas connection the invention makes possible a gradual decrease in the pressure of the liquid entering said container, which eliminates foaming.

According to an advantageous embodiment of the invention the liquid outlet is connected to an operable and closable drainage conduit for alkaline liquid from the container and the drainage conduit is also connected to the connection conduit between the reaction vessel and the container at a point which, starting from the reaction vessel, is located downstream from the point in unfavourable connection conduit where valves or similar arrangements for opening and closing the connection conduit are arranged. In this way unfavorable results of any leakage from the valves in the connection conduit are eliminated.

BRIEF DESCRIPTION OF THE DRAWING FIG.=2 a means for taking samples according to the I present invention and a device for analysing ,the sam ples, connected to the sampling means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sulphate digester l in FIG. 1 is provided with a circulation circuit in which the liquid circulates continuously. A pump 2 and a calorisator 3 are arranged in the conduit 4 of the circulation path. The sampling means which is shown in FIG. {is connected to the circulation circuit by the conduit 5. This device comprises a container 6 which has a liquid inlet 7 at the bottom for the alkaline liquid, which is connected to the circulation circuit of the sulphate digester by the conduit 5. The connection with the circulation circuit can be opened and closed by the three-way valves 8 and 9. The connection conduit 5 contains a filter 10 of reverserinsing type and a cooler 11. The filter is rinsed by water supplied from the conduit '12, the connection between this conduit and the conduit 5 being openable and closable by means of the valve 9. A drainage conduit 13 is also attached to the conduit 5, for the removal of alkaline liquid and rinsing water. The connection between the conduit 13 and the conduit 5 can be opened and closed by the valve 8.

The container 6 also has aliquid outlet 7 at its lower part for the alkaline liquid. In the case shown, therefore, the liquid inlet is also arranged to serve as aliquid outlet. Instead it .is of course possible to use separate means for the inlet and outlet. The liquid is removed from the container 6 either through conduits and 13 or through conduit 5 and the drainage conduit 14 connected to conduit 5 with the openable and closable valve 15. g g I An adjustable gas connection 16 to the outer atmosphere is arranged in the upper part of the container.

The gas connection consists of the a tube 17 whichpenetrates into the container and is provided with a throttle valve 18.

Between the liquid outlet 7 and said opening 16 of the tube is arranged an entrance 34 of a sampling vessel 19. The sampling vessel is provided at the bottom with a valve by which the vessel can be opened and its contents emptied through a conduit 21 into the analysis vessel 22. The sampling vessel may in principle be of any shape and may be located outside the container 6, except for its entrance 34. The entrance must, however, be located at a higher level than the sampling vessel otherwise. The container 6 and the analysis vessel 22 areconnected by conduits 23 and 24, respectively, having openable and closable valves 25 and 26, respectively, to a water container 27 so that the sampling vessel and the analysis vessel can be rinsed and the alkaline liquid in the analysis vessel diluted. The analysis vessel is provided. with an outlet conduit 28 containing the openable and closable valve 29. A device 30 is also connected to the analysis vessel, with the helpof which the liquid can be analysed, and a ventilation conduit The container 6 is also provided with a means in the form of a funnel 31 with 'a tap 32 for supplying samples without using the connection conduit from the sulphate digester. l

The means functions in the following manner: When a sample is to be taken out from the sulphate digester, the connection conduit 5 is opened allthe way from the circulation circuit 4 to the liquid inlet 7 in the container 6. The conduits 12, 13 and 14 are closed off from the conduit 5. The valves 20,25, 26 and 32 are also closed.

The liquid from the digester thus enters the container through the inlet 7 and is permitted to rise to a level 33 located above the entrance 34. The valve 18 is then open all the time to such an extent that sufficient pres sure is retained in the liquid to prevent the formation of foam while at the same time some of the air may leave so that the liquid is permitted to reach the desired level, which means that the pressure in the container 6 is higher than atmospheric pressure. When the liquid has reached the level'33, the connection is closed between the conduit 5 and the circulation circuit 4 by means of the valve 8. The valve 8 is then set so that the connection withthe conduit 13 is open. The conduit 14 is also opened by the valve 15. The liquid in the container 6 can now run out of the container through the liquid outlet 7 and the two drainage conduits 13 and 14. The liquid in the sampling vessel 19, however, will remain. While the liquid is running out of the vessel, the valve 18 is open to such an. extent that air can come in and enable the container 6 to empty itself. While the container 6 is being emptied, the pressure drops to atmospheric pressure. The liquid in the sampling vessel 19, which is an accurately defined volume since it has been possible to avoid foaming, is now emptied into the analysis vessel 22, the valve 29 being kept closed. Since I conduit 24. When the analysis hasbeen performed, the

valve 29 in the conduit 28 is opened and the vessel '22 is cleaned with water from the vessel 27 through the conduits 23 and 24. The container 6 and conduit 5 are also rinsed with water from the container 27 and the filter 10 is reverse-rinsed with water from the conduit 12. When the valves 15, 20, 25 and 26 have been closed and the valve 9 set so that the conduit 12 is shut off and 5 is kept open, the device is ready for a new sample to be taken by adjusting the valve 8 so that the connection to the circulation circuit 4 is opened and the conduit 13 closed.

The deviceis preferably arranged to operate completely automatically with computer control of all the stages described as well as the digestion process in the digester, in the latter case by means of impulses from the analysis device 30.

During periods when no samples are being taken and the connection 5 is shut by the valves 8 and 9, the drainage conduit 14 with open valve 15 can be used to remove leakage coming from the former valves and thus fulfil an important task.

As mentioned previously, separate means may be used for liquid entering and leaving the container 6. SUch an embodiment of the invention is shown with broken lines in F l6. 2. Instead of the conduit 5 between the valve 9 and the liquid inlet or outlet 7, there may be a conduit 5a from the valve 9 to a separate liquid inlet in the container and a conduit 14a from the opening 7 to the valve 15 in the drainage conduit 14. The opening 7 then serves only as an outlet for the liquid.

We claim:

1. Means for taking samples from a reaction vessel containing alkaline liquid under pressure, which comprises a container (6) having inlet and outlet means including a first openable and closable conduit (5) adapted to be connected to the reaction vessel, at least the outlet means being connected to the lower part of the container, an adjustable gas connection (16) in the upper part of the container connected to a gas supply of large volume and lower pressure than the pressure in the reaction vessel, a sampling vessel having an opening at its upper end within the container at a substantial distance above the bottom thereof and at a level between the levels of the outlet means and the gas connection, and analysis apparatus connected to the sampling vessel.

2. Means as claimed in claim 1 in which said gas supply is the atmosphere.

3. Means as claimed in claim 1 in which the first openable and closable conduit includes opening and closing means and the outlet means includes a second openable and closable conduit connected to the first conduit between said opening and closing means and said container. 

1. Means for taking samples from a reaction vessel containing alkaline liquid under pressure, which comprises a container (6) having inlet and outlet means including a first openable and closable conduit (5) adapted to be connected to the reaction vessel, at least the outlet means being connected to the lower part of the container, an adjustable gas connection (16) in the upper part of the container connected to a gas supply of large volume and lower pressure than the pressure in the reaction vessel, a sampling vessel having an opening at its upper end within the container at a substantial distance above the bottom thereof and at a level between the levels of the outlet means and the gas connection, and analysis apparatus connected to the sampling vessel.
 2. Means as claimed in claim 1 in which said gas supply is the atmosphere.
 3. Means as claimed in claim 1 in which the first openable and closable conduit includes opening and closing means and the outlet means includes a second openable and closable conduit connected to the first conduit between said opening and closing means and said container. 